Density-functional calculations of prefactors and activation energies for H diffusion in BaZr O3

Per G. Sundell, Mårten E. Björketun, Göran Wahnström

Resultado de la investigación: Article

73 Citas (Scopus)

Resumen

Density-functional calculations are used to investigate hydrogen diffusion in the solid-state proton conductor BaZr O3. Activation energies and prefactors for the rate of proton transfer and reorientation are evaluated for a defect-free region of this simple cubic perovskite-structured oxide. Both semiclassical over-barrier jumps and phonon-assisted tunneling transitions between sites are considered. It is found that the classical barriers for the elementary transfer and reorientation steps are both of the order of 0.2 eV. The quantum-mechanical zero-point motion effects are found to be sizable, to effectively reduce the barrier heights, and to make the prefactors similar for the transfer and reorientation steps. The Flynn-Stoneham model of phonon-assisted tunneling yields an activation energy of around 0.2 eV and a very small prefactor for proton transfer, whereas the corresponding adiabatic model gives a similar activation energy but a much larger prefactor. It is suggested that the effect of other defects such as dopants has to be included for a proper description of hydrogen diffusion in this material.

Idioma originalEnglish
Número de artículo094301
PublicaciónPhysical Review B - Condensed Matter and Materials Physics
Volumen76
N.º9
DOI
EstadoPublished - 27 sep 2007

Huella dactilar

Density functional theory
Proton transfer
Activation energy
activation energy
retraining
Hydrogen
protons
Defects
Perovskite
Oxides
energy
Protons
defects
hydrogen
Doping (additives)
conductors
solid state
oxides
perovskite

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Citar esto

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abstract = "Density-functional calculations are used to investigate hydrogen diffusion in the solid-state proton conductor BaZr O3. Activation energies and prefactors for the rate of proton transfer and reorientation are evaluated for a defect-free region of this simple cubic perovskite-structured oxide. Both semiclassical over-barrier jumps and phonon-assisted tunneling transitions between sites are considered. It is found that the classical barriers for the elementary transfer and reorientation steps are both of the order of 0.2 eV. The quantum-mechanical zero-point motion effects are found to be sizable, to effectively reduce the barrier heights, and to make the prefactors similar for the transfer and reorientation steps. The Flynn-Stoneham model of phonon-assisted tunneling yields an activation energy of around 0.2 eV and a very small prefactor for proton transfer, whereas the corresponding adiabatic model gives a similar activation energy but a much larger prefactor. It is suggested that the effect of other defects such as dopants has to be included for a proper description of hydrogen diffusion in this material.",
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Density-functional calculations of prefactors and activation energies for H diffusion in BaZr O3. / Sundell, Per G.; Björketun, Mårten E.; Wahnström, Göran.

En: Physical Review B - Condensed Matter and Materials Physics, Vol. 76, N.º 9, 094301, 27.09.2007.

Resultado de la investigación: Article

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T1 - Density-functional calculations of prefactors and activation energies for H diffusion in BaZr O3

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AU - Björketun, Mårten E.

AU - Wahnström, Göran

PY - 2007/9/27

Y1 - 2007/9/27

N2 - Density-functional calculations are used to investigate hydrogen diffusion in the solid-state proton conductor BaZr O3. Activation energies and prefactors for the rate of proton transfer and reorientation are evaluated for a defect-free region of this simple cubic perovskite-structured oxide. Both semiclassical over-barrier jumps and phonon-assisted tunneling transitions between sites are considered. It is found that the classical barriers for the elementary transfer and reorientation steps are both of the order of 0.2 eV. The quantum-mechanical zero-point motion effects are found to be sizable, to effectively reduce the barrier heights, and to make the prefactors similar for the transfer and reorientation steps. The Flynn-Stoneham model of phonon-assisted tunneling yields an activation energy of around 0.2 eV and a very small prefactor for proton transfer, whereas the corresponding adiabatic model gives a similar activation energy but a much larger prefactor. It is suggested that the effect of other defects such as dopants has to be included for a proper description of hydrogen diffusion in this material.

AB - Density-functional calculations are used to investigate hydrogen diffusion in the solid-state proton conductor BaZr O3. Activation energies and prefactors for the rate of proton transfer and reorientation are evaluated for a defect-free region of this simple cubic perovskite-structured oxide. Both semiclassical over-barrier jumps and phonon-assisted tunneling transitions between sites are considered. It is found that the classical barriers for the elementary transfer and reorientation steps are both of the order of 0.2 eV. The quantum-mechanical zero-point motion effects are found to be sizable, to effectively reduce the barrier heights, and to make the prefactors similar for the transfer and reorientation steps. The Flynn-Stoneham model of phonon-assisted tunneling yields an activation energy of around 0.2 eV and a very small prefactor for proton transfer, whereas the corresponding adiabatic model gives a similar activation energy but a much larger prefactor. It is suggested that the effect of other defects such as dopants has to be included for a proper description of hydrogen diffusion in this material.

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